The present invention relates to the field of munitions, and more particularly to an improved design for a secondary self-destruct fuze that functions in the event the primary fuze mode fails to function, and that meets the design requirements for low cost, highly producible, and a non-spin/low velocity operating environment.
Dual Purpose Improved Conventional Munitions (DPICM) must have either a self-destruct capability or they must show dud rates not to exceed 1 in 500 as an operational requirement. To this end, several engineering studies were undertaken in an attempt to address the low reliability of the conventional M223 mechanical fuze. However, these studies did not change the basic design of the M223 mechanical fuze. Instead, they generally considered modifying the materials and the manufacturing processes to reduce the dud rate problem.
Conventional designs proposed the development of a hybrid electromechanical fuze which is relatively complex with approximately 40 to 50 parts, with a costly production line. In addition, the no-spin/low velocity operational environments of grenades jeopardize the fuze reliability. Several projectiles have unique operational requirements that the current fuze design might not meet readily.
Some of the concerns facing current self-destruct fuze designs are listed below:
(1) The threads between the arming screw and the weight can be overtorqued.
(2) The fuze components may suffer collateral damage during ejection from the carrier.
(3) The fuze may impact the ground at oblique angles and the firing pin might not provide sufficient energy to the detonator.
(4) The fuze may operate poorly in a no-spin/low velocity environment.
Therefore, there is a still unsatisfied need for a fuze which, among other features, solves the no-spin/low velocity environment, significantly reduces the number of components, improves producibilty, and increases the operational reliability of the primary arming mode.
Several engineering studies were conducted in the past two decades in an attempt to address the low reliability of existing mechanical fuzes. Although these xe2x80x98mechanical onlyxe2x80x99 solutions did improve the overall functional reliability of the fuze, there is still room for an improved design that fully addresses the no-spin/low velocity operational environment, and that significantly reduces the dud rate to the present ordnance requirements for self destruct fuzing of grenades.
A design that proposes a secondary self-destruct electrical mode of operation is described in U.S. Pat. No. 5,387,257. While the patented fuze provides an improvement in the relevant field, the activation of this self-destruct mode requires forces that are not available from non-spin/low velocity environment. In addition, it""s high cost makes it unaffordable.
The present invention contemplates an improved design for a secondary self-destruct fuze that functions in the event the primary fuze mode fails to function, and that meets the design requirements for low cost, highly producible, and a non-spin/low velocity operating environment.
The fuze offers several features and advantages, among which are the following:
(1) It significantly improves the performance of traditional M223 mechanical fuzes by providing a redundant mode of operation, which adds a self-destruct capability and leads to a tactical destruction of the grenade at impact angles greater than 60 degrees relative to the vertical, on all types of terrain.
(2) It significantly simplifies conventional designs and the production process. It uses the main firing mode of the M223 fuze, and adds a few components to the M223 fuze, to add a relatively simple secondary mode of operation through a back up independent firing pin. These additional components can be made of readily available materials that are fabricated for example, by means of stamping, die casting, or precision molding techniques.
(3) It solves the functional reliability problems when operating in a no-spin/low spin environment.
(4) It uses a unique low cost mechanical/pyrotechnic design to provide a high functional reliability, in almost all operating environments. It uses a unique aerodynamic safety release (ASR) to function the secondary mode feature providing self-destruct fuzing capability.
(5) It meets all MIL-STD-1316D standards.
(6) It is compatible with almost all grenade configurations.
(7) It provides a self destruct delay of between 30-45 seconds.
The foregoing and other features and advantages of the present invention are realized by a fuze that includes an improved slide assembly that incorporates a pyrotechnic delay mechanism with a minimum number of components. The fuze operates in two modes. In a primary mode, the fuze can function similarly to a conventional M223 fuze. In a secondary, self-destruct mode, a pyrotechnic delay mechanism is initiated. The slide assembly is comprised of an aerodynamic safety release (ASR), a safety pin, a rotational firing pin fitted with a resilient member such as a spring, an M55 detonator, a pyrotechnic initiator, a pyrotechnic delay mix and an end cap.
In use, the fuze is fitted to a munition or grenade. As the grenade is dispensed from its carrier, a grenade stabilizer starts to oscillate and sense drag. The oscillation and drag results in an arming screw and an inertial weight to back out from a slide assembly, allowing the slide assembly to move to an in-line position relative to a main M55 detonator in-line with the arming screw (firing pin). Concurrently, the unique aerodynamic safety release is lifted in the upward direction under the force of the airstream, releasing the safety pin. This releases the rotational firing pin, which forces the rotational firing pin to contact the pyrotechnic initiator.
The pyrotechnic delay mix burns to the end cap and propagates to the M55 detonator. The initiation of the M55 detonator causes the fuze to function in the primary mode or, if for any reason the primary mode fails to function the grenade, the grenade is rendered safe to handle by the secondary mode.